Summation Problem

Hi all,
I have a homework assignment from my calc. 2 class and one of the problems is really difficult for me. I am supposed to come up with a general formula for the summation from k = m to n of [(-1)^k^2][x^2k].
I don't want the answer, but I don't know where to begin.
I'm pretty sure I have to manipulate it into a simple geometric sum with only k as an exponent, but the algebra is working up my nerves.

Hi all,
I have a homework assignment from my calc. 2 class and one of the problems is really difficult for me. I am supposed to come up with a general formula for the summation from k = m to n of [(-1)^k^2][x^2k].
I don't want the answer, but I don't know where to begin.
I'm pretty sure I have to manipulate it into a simple geometric sum with only k as an exponent, but the algebra is working up my nerves.